索绪尔区分了语言研究中的共时性和历时性。然而,这两种研究方法有时候相互关联。某些共时的变异可以通过历时的演化来加以解释。例如,15至17世纪在英国发生的元音大转移,印欧语系部分语言中一些元音的历史同化,19世纪日耳曼语言中发生的两次辅音转移,以及汉语中出现的一些例证充分说明了这个问题。只要我们细心观察,会发现语言是有规律性的。这种语言知识有助于学习者更好地了解和掌握目的语。 Saussure distinguishes between synchronicity and diachronicity in language studies. However, the two methods are sometimes interrelated. Some of the synchronic variations can be explained by the evolution over time. For example, the vowel shift in the United Kingdom between the 15th and 17th centuries, the historical assimilation of some vowels in some Indo-European languages, the two consonant shifts that occurred in 19th-century Germanic languages, and some illustrations in Chinese this problem. As long as we observe carefully, we can find that the language is regular. This language knowledge helps learners to understand and master the target language better.